Anodic treatment of uranium



AN ODIC TREATMENT OF URANIUM Morris Kolodney, New York, N. Y., assignor to the United States of America as represented by the Umted States Atomic Energy Commission N Drawing. Application May 12, 1948 Serial No. 26,712

16 Claims. (Cl. 204-15) This invention relates to a method for dissolving metals, and more particularly, to a method for uniformly dissolving uranium.

It is often desirable to quickly and etficiently remove acontrolled amount of metal from a uranium object and/ or to obtain a smooth, uniform surface.

However, when uranium is dissolved chemically in a strong acid such as nitric or hydrochloric acid, the rate of solution is not uniform over the metal surface, pitting results and the reaction may become violent.

It is, therefore, the primary object of this invention to provide a method for uniformly, efficiently and effectively dissolving uranium.

It is a further object of this invention to provide a method for treating uranium objects so that they will have a clean, smooth, uniform surface.

It is a still further object of this invention to provide a method for dissolving uranium at a controlled rate so as to remove a predetermined amount of uranium and obtain a surface which is clean, smooth, uniform and free from all pitting.

Still further objects and advantages of this invention will be apparent from the following description.

The objects of this invention are achieved by the process of making the uranium objects anodic in an acid solution electrolyte containing phosphate and nitrate ions.

More specifically, the phosphate ions in the electrolyte may be furnished by an acid phosphate solution such as an aqueous orthophosphoric acid and the nitrate ions may be furnished by a nitrate of ammonium or a light alkali metal.

The following example illustrates the presently preferred embodiment of the invention. It is given for the purpose of illustration only and is not intended to be limiting on its spirit or scope.

Example 100 cubic centimeters of 85 percent orthophosphoric acid and 100 grams of sodium nitrate are made up with water to a volume of 500 cubic centimeters. A block of uranium approximately 2 inches by 2 inches by 1 inchand a block of stainless steel of about the same dimensions are connected respectively to anode and cathode leads. The metal blocks are lowered into the electrolyte and placed about an inch apart. Potential is applied to the current leads and the current density is adjusted to 0.65 ampere per square inch. In about 5 minutes the uranium object has a smooth surface free from all pitting and ridge formation. This operation is carried out at a uniform and controlled rate at 100 percent or nearly 100 percent efiiciency uniformly removing about 0.4 mil from all surfaces of the uranium object. It is thought that the uranium is dissolved at this uniform rate because the nitrate ions are the active dissolving agents while the phosphate ions form soluble complex compounds and thus prevent film formation on the anode.

The method of carrying out the invention illustrated in the above example may be varied in many ways.

Patented Feb. 3, 3.959

by acid phosphates other than orthophosphoric acid. The

nitrate ions may be supplied by ammonium, lithium, sodium, or potassium nitrates.

Although the amount of the phosphate and nitrate ions may be varied, it is desirable to have an appreciable concentration of both of these ions to etficiently and rapidly remove the uranium. For example, when uranium is made anodic in a solution containing a light alkali metal nitrate such as sodium nitrate and an acid such as nitric acid, but containing no source of phosphate ions, the uranium is not removed, but becomes passive. When it is made anodic in a solution containing a light alkali metal nitrate such as sodium nitrate and an acid such as acetic acid, excessive frothing occurs. When a solution containing only nitrate ions is used as the electrolyte, a yellow precipitate which is probably uranyl hydroxide, forms at the cathode.

In like manner, when the uranium object is made anodic in a solution containing equal volumes of orthophosphoric acid and water, but no source of nitrate ions, the rate of removal of uranium is considerably decreased. For example, with this solution as the electrolyte, a current density of about 2 amperes per square inch will remove 5 mils of uranium in about an hour. The relative efiiciency of this, as compared with the method of this invention illustrated in the example, may be observed when it is noted that in the example a current density of 0.65 ampere per square inch removed about 0.4 mil in five minutes.

The method of. the invention as presented in the example may be modified in other ways. The container need not be of Pyrex glass but may be of any material which is not appreciably dissolved by the electrolyte. In like manner, the cathode need not be of stainless steel but may be of any metal which is not appreciably soluble in the electrolyte.

The anode current density at room temperature may range from 0.1 to 1.0 ampere per square inch. When the current density is set at any value within this range, the uranium, treated according to the method of this invention, dissolves at virtually percent current efliciency. The surface of a uranium object, treated in this manner, is smooth and uniform. It is of course possible to vary the rate at which the uranium is removed by changing the current density, and to vary the amount of uranium removed by changing either or both the current density and the time for which the current is applied.

Because other modifications and embodiments are possible without departing from the spirit or scope of this invention, it is to be understood that the invention is not to be limited except as indicated in the appended claims.

What is claimed is:

1. The method of elfectively and efficiently dissolving uranium which comprises making the uranium anodic in a phosphoric acid solution containing nitrate ions furnished by a nitrate of the class consisting of ammonium, lithium, sodium, and potassium nitrates.

2. The method of treating uranium which comprises making the uranium anodic in an aqueous solution of phosphoric acid and a nitrate of the class consisting of ammonium, lithium, sodium, and potassium nitrates.

3. The method of treating uranium which comprises .making the uranium anodic in an aqueous solution phosphoric acid and sodium nitrate.

5. The method of treating uranium which comprises making the uranium anodic in an aqueous solution of phosphoric acid and potassium nitrate.

at current densities of from 0.1 to 1.0 ampere per square 6. The method of treating a uranium object in order 7 to remove a predetermined amount of uranium and to obtain a clean, smooth, uniform surface which comprises making the uranium anodic for a predetermined period of time in an aqueous solution containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and 100 to 200 grams of a nitrate of the class consisting of ammonium, lithium, sodium, and potassium nitrates.

7. The method of treating a uranium object in order to remove a predetermined-amount of uranium and to obtain a clean, smooth, uniform surface which comprises making the uranium anodic for apredetermined period of time in an aqueous solution containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and 100 to 200 grams of ammonium nitrate.

8. The method of treating a uranium object in order to remove a predetermined amount of uranium and to obtain a clean, smooth, uniform surface which comprises making the uranium anodic for a predetermined period of time in an aqueous solution containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and 100 to 200 grams of sodium nitrate.

9. The method of treating a uranium object in order to remove a predetermined amount of uranium and to obtain a clean, smooth, uniform surface which comprises making the uranium anodic for a predetermined period of time in an aqueous solution containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and 100 to 200 grams of potassium nitrate.

10. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic, at current densities of from 0.1 to 1.0 ampere per square inch, in aqueous phosphoric acid solutions containing nitrates of the class consisting of ammonium, lithium, sodium, and potassium nitrates.

11. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic,

inch, in aqueous solutions containing in each liter 100 to 500 cubic centimeters of percent orthophosphoric acid and to 200 grams of ammonium nitrate.

12. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic, at current densities of from 0.1 to 1.0 ampere per square inch, in aqueous solutions containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and from 100 to 200 grams of sodium nitrate.

13. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic, at current densities of from 0.1 to 1.0 ampere per square inch, in aqueous solutions containing in each liter 100 to 500 cubic centimeters of 85 percent orthophosphoric acid and 100 to 200 grams of potassium nitrate.

14. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic, at a current density of 0.65 ampere per square inch, in aqueous solutions containing in each liter 200 cubic centimeters of 85 percent orthophosphoric acid and 200 grams of ammonium nitrate.

15. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic,

at a current density of 0.65 ampere per square inch, in aqueous solutions containing in each liter 200 cubic centimeters of 85 percent orthophosphoric acid and 200 grams of sodium nitrate.

16. The method of dissolving uranium at a uniform and controlled rate and obtaining a clean, smooth, uniform surface which comprises making the uranium anodic, at a current density of 0.65 ampere per square inch, in aqueous solutions containing in each liter 200 cubic centimeters of 85 percent orthophosphoric acid and 200 grams of potassium nitrate.

References Cited in the file of this patent 1 UNITED STATES PATENTS Davenport Jan. 6, 1931 Jernstedt Feb. 22, 1949 OTHER REFERENCES 

1. THE METHOD OF EFFECTIVELY AND EFFICIENTLY DISSOLVING URANIUM WHICH COMPRISES MAKING THE URANIUM ANODIC IN A PHOSPHORIC ACID SOLUTION CONTAINING NITRATE IONS FURNISHED BY A NITRATE OF THE CLASS CONSISTING OF AMMONIUM, LITHIUM, SODIUM, AND POTASSIUM NITRATES. 